digitalmars.D - Rationale for TLS being the default

Couldn't find it at the website. What's the advantage of going the other way
(compared to C's defaulting to globals and the __thread keyword which is also
used by some D1 guys in a modified dmd)?
Might be good to put it into something like
http://www.digitalmars.com/d/2.0/migrate-to-shared.html